Arc chute utilizing staggered u-shaped conductive members



May 13, 1952 c. R. PETER 2,596,865

ARC CHUTE UTILIZING STAGGERED U SHAPED CONDUCTIVE MEMBERS Filed July 3,1950 Patented May 13, 1952 ARC CHUTE UTILIZING STAGGERED U-SHAPEDCONDUCTIVE MEMBERS Charles R. Peter, Wauwatosa, Wis., assigner toAllis-Chalmers Manufacturing Company, Milwaukee, Wis.

Application July 3, 1950, Serial No. 171,843

4 Claims. 1

This invention relates in general to electric switching devices and inparticular to electric arc extinguishing means for such switchingdevices.

It is a principal object of this invention to provide an improved arcextinguishing structure in which series connected arcs are successivelydrawn between a plurality of arc extinguishing members.

It is an additional object of this invention to provide an areextinguishing structure in which series connected arcs are successivelydrawn and the series arcs are confined within a portion of the arcextinguishing structure,

Objects and advantages other than those outlined above will be readilyapparent from the following detailed description when read in connectionwith the accompanying drawing, in which:

Fig. l is a side view of a switching device embodying the presentinvention;

Fig. 2 is an enlarged sectional view through the arc chute of the deviceillustrated in Fig. 1;

Fig. 3 is a sectional view taken along line III-III of Fig. 2; and

Fig. 4 is a development View looking in the direction of arrow IV ofFig. 2.

Referring to Fig. 1, a switching device embodying the present inventioncomprises a pair of relatively movable current carrying contacts II, I2between which an arc may be formed upon separation thereof. Contact IIis connected through a curved conductive bar I3 to a terminal stud I4,while contact I2 is connected through a conductive member I5 and ailexible lead IB to a terminal stud I1. Studs I4, I1 representconnections to a circuit which the device is to interrupt. y The xedcontact assembly is supported on a suitable insulating base I8 throughstud I4. Secured to bar I3 is a U-shaped bridging member 28 of laminatedmagnetic material which cooperates in a well known manner with bar I3 toform a blowout assembly for impelling the arc formed upon separation ofcontacts II, I2 into the arc extinguishing chute. This blowout assemblymay be dispensed with if the heat generated by formation of the arcprovides sufficient impelling force to blow the arc into the chute.

Contact I2 is movable into and out of engagement with contact II bymovement imparted to a shaft 29. Shaft 29 is journaled in brackets 3Isecured to base I8 by screws 32 and is given rotational movement bysuitable actuating means (not shown) such as an electromagnet. Clockwiserotation oi shaft 29 moves contact I2y in a clockwise direction from theposition shown to separate contacts II, I2 and form an arc therebetween.

As shown in Figs. 2 4, the arc chute 4I comprises a pair of spaced sidewalls 42, 43 located on opposite sides of the path of movement of thearc. Chute 4I is provided with an intermediate section 44 adjacentcontacts Il, I2 wherein the arc is formed and an exhaust section 45between the top portions of side walls 42, 43. End members 46, 41maintain the proper spacing between side walls 42, 43 and serve to connethe arc within the chute 4I. The arc chute assembly is rigidly securedtogether by bolts 43 and nuts 49 extending through side walls 42, 43 andend members 46, 41.

An insulating member 5I is disposed midway between side walls 42, 43 andextends substantially parallel to walls 42, 43. Recesses 52, 53 areprovided in end members 46, 41 respectively. to receive the ends ofmember 5I. Two pluralities of U-shaped conductive members 54a through54f andy 55a through 55j are secured to side walls 42, 43 and form tworows disposed in the general lengthwise direction of the arc, the row ofmembers 54 being staggered with respect to the row of members 55.Members 54, 55 may be made of any suitable heat resistant conductor suchas steel or brass. As indicated on a representative conductive member54j in Fig. 2, each conductive member comprises a pair of spaced legportions 56, 51 extending in the general direction of movement of thearc and a curved portion 58 joining leg portions 56, 51 in theintermediate section of the chute.

Members 54, 55 abut their respective side walls along an edge extendingfrom the bight of the U to the exhaust section of the chute. Some of theconductive members 54, 55, and preferably all of them, increase in depthin a direction perpendicular tothe direction of movement of the arc andto the lengthwise direction of the arc, i. e., away from the side wallsto which they are secured and toward the insulating member 5I, from thebight of the U, and are adjacent to or abut the insulating member 5I inthe exhaust section of the chute. This increase in depth of members 54,55 forms edges 6 I, as shown in Fig, 3, upon which the varc impingesduring its movement in chute 4I. As shown in the drawing, members 54, 55may be set in recesses 62 in their respective side walls 42, 43, and ifmembers 54, 55 abut insulating member 5I in the exhaust section of thechute, recesses 63 may be provided in member 5I to receive the abuttingends.

The arc chute assembly is detachably mounted with respect to contactsII, I2 by any suitable known means (not shown) to provide easy removalfor replacement or repair.

Upon separation of contacts II, I2, an arc is formed therebetween in theintermediate section 44 of chute 4I. The heat generated by this arcimpels the arc upwardly in the chute and the blowout assembly describedabove furnishes additional impelling force. The are in moving upward rstimpinges on conductivemember 55a between contact I I and member 55a, andas contact I2 continues to move, the arc is extended until it impingeson member 55h. At this time the arc will exist in the form of a shortarc between contact I I and member 55a, another short arc betweenadjacent leg portions of adjacent members 55a, 55h, and another shortarc between member 5519 and contact I2. Continued movement of contact I2causes the arc to successively impinge on the succeeding conductivemembers 55C, 55d, 55e, 55j, thereby successively drawing a plurality ofshort arcs between adjacent leg portions of adjacent conductive members55.

As these short arcs move toward the exhaust section of the chute, thedistance between adjacent leg portions of adjacent members 55 increases,thereby progressively increasing the resistance of the air gaps throughwhich the short arcs must travel and hence reducing the magnitude of thearc current and hastening the extinction of the arc. In addition, thearc current ilowing in conductive members 55 meets a path of continuallyincreasing resistance as the short arcs move in the chute, owing to theincreasing distance in the conductive members through which the arccurrent must flow. This increasing resistance further progressivelyreduces the arc current and thereby further speeds the extinction or"the arc.

The plurality of short arcs continue to travel in chute 4I, encounteringpaths of progressively increasing resistance, until the arcs areextinguished in the exhaust section of the chute.

Although in the above described operation of the arc chute, it wasassumed that the arc impinged on member 55a upon separation of contactsII, I2, it will be readily apparent that the arc might impinge on member54a upon separation of the contacts and then be caused to successivelyimpinge on members 54h, 54o, 54d, 54e, 54j, without changing theprinciple of operation of the arc extinguishing means.

Insulating member 5I serves to separate members 54 from members 55 andthereby confine the short arcs between either adjacent members 54 oradjacent members 55.

Members 54 are staggered with respect to members 55 to provide a maximumarc extinguishing effect regardless of the size of the arc current. Whenthe interrupted current is of suincient magnitude, the resultant arewill produce a region of conductive gas extending around insulatingmember 5I and in contact with both rows of members 54, 55. If members54, 55 were aligned with each other, there would be no increase in thenumber of series arcs obtained in the chute with a current of thismagnitude with respect to the number of arcs obtained with smallercurrents. However, when members 54, 55 are staggered with respect toeach other, as shown, if the arc current is of sufficient magnitude toproduce an arc extending between staggered members 54, 55, around member5I, the arc current must ow in a zigzag path between leg portion ofmembers 54 and leg portions of members 55, thereby nearly doubling thenumber of series arcs with respect to the number of series arcs whichwould be available if members 54, `55 were aligned. Also, the staggeredrelation of members 54, 55 insures that there is no point throughout thelength of the arc at which the arc does not encounter a U-shaped shortcircuiting member, 54, 55, thereby insuring that the arc impinges on aconductive member shortly after being drawn.

Although but two embodiments of the invention have been shown anddescribed, it will be apparent to those skilled in the art that variousmodifications may be made therein without departing from the spirit ofthe invention or from the scope of the appended claims.

It is claimed and desired to secure by Letters Patent:

l. Means for extinguishing an electric arc movable in a predeterminedgeneral direction comprising an arc chute provided with a pair of spacedside walls located on opposite sides of the path of movement of said arcand having an intermediate section wherein said arc is formed and anexhaust section, an insulating member disposed between said side wallsin said exhaust section and extending parallel to said side walls, and aplurality of U-shaped conductive members on which different portions ofsaid arc successively impinge, said members being secured to said sidewalls and forming two rows disposed in the general lengthwise directionof said arc, the members of one of said rows being staggered in saidlengthwise direction with respect to the members of the other of saidrows, each said conductive member comprising a pair of spaced legportions extending in the general direction of movement of said arc andhaving a curved portion joining said leg portions in said intermediatesection to form a U, the said conductive members secured to one of saidwalls abutting said one wall in said intermediate section and increasingin depth from the bight of said U in a direction toward said insulatingmember and abutting said insulating member in the exhaust section ofsaid chute.

2. Means for extinguishing an electric arc movable in a predeterminedgeneral direction comprising an arc chute provided with a pair of spacedside walls located on opposite sides of the path of movement of said arcand having an intermediate section wherein said arc is formed and anexhaust section, an insulating member disposed between said side wallsin said exhaust section and extending parallel to said side walls, and aplurality of U-shaped conductive members on which different portions ofsaid arc successively impinge, said members being secured to said sidewalls and forming two rows disposed in the general lengthwise directionof said arc, the members of one of said rows being staggered in saidlengthwise direction with respect to the members of the other of saidrows, each said conductive member comprising a pair of spaced legportions extending in the general direction of movement of said arc andhaving a curved portion joining said leg portions in said intermediatesection to form a U, the said conductive members secured to one of saidwalls abutting said one wall in said intermediate section and increasingin depth from the bight of said U in a direction toward said insulatingmember.

3. Means for extinguishing an electric arc movable in a predeterminedgeneral direction comprising an arc chute provided with a pair of spacedside walls located on opposite sides of the path of movement of said arcand having an intermediate section wherein said arc is formed and anexhaust section, an insulating member disposed between said side wallsin said exhaust section and extending parallel to said side walls, and aplurality of U-shaped conductive members on which different portions ofsaid arc successively impinge, said members 'being secured to said sidewalls and forming two rows disposed in the general lengthwise directionof said arc, the members of one of said rows being staggered in saidlengthwise direction with respect to the members of the other of saidrows, each said conductive member comprising a pair of spaced legportions extending in the general direction of movement of said arc andhaving a curved portion joining said leg portions in said intermediatesection to form a U, each said conductive member abutting one of saidside walls in said intermediate section and increasing in depth from thebight of said U in a direction toward said insulating member andabutting said insulating member in the exhaust section of said chute.

4. Means for extinguishing an electric arc movable in a predeterminedgeneral direction comprising an arc chute provided with a pair of spacedside walls located on opposite sides of the path of movement of said arcand having an intermediate section wherein said arc is formed and anexhaust section, an insulating member disposed midway between said sidewalls in said exhaust section and extending parallel to said side walls,and a plurality of U-shaped conductive members on which differentportions of said arc successively impinge, said members being secured tosaid side walls and forming two rows disposed in the general lengthwisedirection of said arc, the members of one of said rows 'being staggeredin said lengthwise direction with respect to the members of the other ofsaid rows, each said conductive member comprising a pair of spaced legportions extending in the general direction of movement of said arc andhaving a curved portion joining said leg portions in said intermediatesection to form a U, each said conductive member abutting one of saidside walls in said intermediate section and increasing in depth from thebight of said U in a direction toward said insulating member andabutting said insulating member in the exhaust section of said chute.

CHARLES R. PETER.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 2,353,729 Jensen July 18, 19442,356,040 Ellis et al. l Aug. 15, 1944 2,408,352 'Iitus Sept. 24, 19462,446,027 Scott, Jr July 27, 1948

